Determination of landau fermi-liquid parameters in si-MOSFET systems

We analyze experimental data in order to evaluate Landau Fermi-liquid parameters. By using row data of recent Shubnikov-de Haas measurements, we derive, as a function of the electron density n _s, results for the compressibility mass of the charged two-dimensional electron gas. The compressibility mass is nearly equal to the transport mass even in the density region where the transport mass has the tendency to diverge. We conclude that Landau Fermi-liquid parameter F ₀^s (n _s) is nearly independent of electron density and close to zero. This result is derived for silicon (100) and silicon (111) surfaces. We also obtain the dependence of F ₁^s (n _s), determining the transport mass, and of F ₀^a (n _s), determining the spin susceptibility. The text was submitted by the authors in English.     

Determination of landau level lifetimes in n-GaAs

The lifetime of electrons in the first excited Landau level of n-GaAs is determined from a combination of measurements of far infrared cyclotron resonance induced absorption and conductivity change. Values of T₁ of the order of 10^?8s for densities of excited electrons of 10¹¹ cm^?3 and a temperature dependence of T^?2.7 are found. An upper limit for the N = 0 Landau level to donor recombination time of the order of 10^?9s was derived from pulsed conductivity measurements.     

Calculation of Landau's fermi-liquid parameters in pure neutron matter

The Landau parameters F₀, F₁, G₀ and G₁ have been calculated in pure neutron matter including the interaction induced by exchange of density-density and spin-density excitations at densities up to k_F = 2.5 fm^?1. The main effect of the induced interaction is to make the matter more incompressible.     

Experimental determination of magnetic landau parameters in ErRh4B4

From d.c. magnetization data obtained between 0.45 and 13 K we derive the bare Curie temperature, the temperature dependence of the paramagnetic susceptibility, and the coefficients of the higher order terms in the Landau expansion of the magnetic free energy for ErRh₄B₄. We find the unexpected result that the fourth order term is small or zero. Consequently the sixth order term plays the dominant role in stabilizing the magnetic phase.     

Spontaneous breakdown of translational symmetry in quantum hall systems: crystalline order in high landau levels

We report on results of systematic numerical studies of two-dimensional electron gas systems subject to a perpendicular magnetic field, with a high Landau level partially filled by electrons. Our results are strongly suggestive of a breakdown of translational symmetry and the presence of crystalline order in the ground state. This is in sharp contrast with the physics of the lowest and first excited Landau levels, and in good qualitative agreement with earlier Hartree-Fock studies. Experimental implications of our results are discussed.     

Phonon excitations of composite-fermion landau levels

Phonon excitations of fractional quantum Hall states at filling factors nu = 1/3, 2/5, 4/7, 3/5, 4/3, and 5/3 are experimentally shown to be based on Landau-level transitions of composite fermions. At filling factor nu = 2/3, however, a linear field dependence of the excitation energy in the high-field regime rather hints towards a spin transition excited by the phonons. We propose to explain this surprising observation by an only partially polarized 2/3 ground state, making the energetically lower lying spin transition also allowed for phonon excitations.     

Ultrasonic study of spin-splitting of landau levels in bismuth

A study has been made, using ultrasonic quantum oscillations, of the spin-splitting factor of electrons and of holes in bismuth with the magnetic field direction varied in the XZ plane. The results are consistent with the general picture of spin-splitting in bismuth.     

Recombination radiation from landau states in impactionized GaAs

Recombination radiation from Landau states in impact ionized high-purity GaAs has been observed. The narrow band (～ 3 cm^?1) emission has been magnetically tuned from 80–120 cm^?1, and used to observe rotational transitions in water vapor.     

Conductivity of a half filled landau level

It is shown that the thermodynamic instability at the half filling of L1 leads to the vortex lattice formation with the electronic spectrum analogous to that of graphene with two Dirac-Fermi points on Brillouin cell boundary. This result is used for the explanation of the observed current generated by a surface acoustic wave in the heterostructure on the surface of piezoelectric GaAs. Using the existence of two Fermi points instead of a Fermi surface suggested in the previous theoretical works, permit the explanation of the experimental results.     

Determination of limiting parameters of multiple-beam electron-optical systems for diagnostics of semiconductor structures

The factors limiting the possibilities of electron probe systems for diagnostics of semiconductor structures are discussed. Their effect on instrument characteristics, i.e., efficiency, resolution, and data quality, are determined. The correlation between these characteristics is considered to develop an electron probe system for a particular application, i.e., defect detection with a set of characteristics best corresponding to this specific problem, is determined.     

Nonthermal broadening of landau levels in n-type indium antimonide

We have studied nonthermal broadening of Landau levels in n-InSb with carrier densities of 3·10¹⁵−10¹⁷ cm⁻³. We show that scattering on dopant impurities causes nonthermal broadening in n-InSb. We determine the variations in dopant density in our n-InSb samples. Ryazanskii State Teachers University. Ryazanskii Scientific Research Technological University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 90–92, August, 1997.     

Determination of the spectral parameters of doped nematochiral composites for optical switching systems

A simple equation describing the optimum relation of the parameters of doped nematochiral cells for use in real systems of switching and limiting of laser radiation is obtained based on analytical estimates. The adequacy and feasibility of the derived relation is confirmed experimentally.     

Measurement of landau coefficients in ferroelectrics using nonlinear dielectric spectroscopy

A method of measuring the phenomenological Landau-Ginzburg coefficients in an expansion of the free energy of ferroelectrics near the phase transition is proposed. This method is based on simultaneously recording five Fourier components of the current response to a sinusoidal voltage as a function of temperature. An analysis is made of a specific application of the method to Langmuir-Blodgett ultrathin ferroelectric films.     

Algebraic investigations in landau model of structural phase transitions

First we introduce the basic notions of the theory of permutation representations: stabilizers, orbits, stable subsets and strata. Then we consider the relation between permutation and linear representations which lead to some formulae connecting subduction coefficients, Clebsch-Gordan coefficients, and dimensions of stability spaces. This relation also leads to the concept of suborbits. Epikernels, the subgroups which are stabilizers of vectors of irreducible subspaces (either on the complex or on the real field) — are, studied and several theorems about them are proved. Further we consider the relation between epikernels, stability spaces and strata for subspaces irreducible on the real field as compared with subspaces irreducible on the complex field. Finally, the exomorphism is defined with use of permutation representations. The vectors of irreducible subspaces and corresponding epikernels (their stabilizers) for real ireps (representations irreducible on the real) of the classical crystal point groups are given in the appendix.     

Transition in a Luttinger liquid with two-level impurities to the fermi-liquid state

The mechanisms leading to instability of the non-Fermi-liquid state of a Luttinger liquid with two-level impurities are proposed. Since exchange scattering in 1D systems is two-channel scattering in a certain range of parameters, several types of non-Fermi-liquid excitations with different quantum numbers exist in the vicinity of the Fermi level. These excitations include, first, charge density fluctuations in the Luttinger liquid and, second, many-particle excitations due to two-channel exchange interaction, which are associated with band-type as well as impurity fermion states. It is shown that mutual scattering of many-particle excitations of various types leads to the emergence of an additional Fermi-liquid singularity in the vicinity of the Fermi level. The conditions under which the Fermi-liquid state with a new energy scale (which is much smaller than the Kondo temperature) is the ground state of the system are formulated.     

Determination of interfacial parameters in fiber-polymer systems from pull-out test data using a bilinear bond law

We propose a new model for characterization of strength properties of fiber-polymer interfaces by means of a single fiber pull-out test. Our model is based on shear-lag analysis using a bilinear bond law (stress–slip relationship) which, in turn, is a simplified representation of the true stress behavior as a function of strain for cold-drawing polymers. According to this law, the fiber-polymer interface is subjected to the following successive processes: (1) linear loading within the elastic region; (2) yielding and subsequent bond strengthening with increasing strain; (3) local debonding and interfacial crack propagation along the interface; (4) post-debonding friction. Both crack propagation and extension of the yielded zone can be stable and unstable, depending on the values of interfacial parameters and the load applied to the free fiber end. The procedure of construction of theoretical force–displacement curves for a pull-out test is described in detail. Theoretical curves exhibit such features as multiple kinks and non-linear regions, whose positions and shape are related to interfacial parameters. By fitting experimental curves with theoretical ones, these parameters can be determined for each separate pull-out specimen. Practical examples are provided for basalt fiber–polypropylene and glass fiber–polypropylene specimens.     

Neutron excitation of landau and collective modes in a magnetized plasma

Summary The response function for magnetic neutron scattering off electrons forming a one-component plasma, or jellium model, subject to a steady magnetic field, is calculated in the semi-classical limit in which Boltzmann statistics apply to the electron states. A complete expression for the response of an ideal plasma is given in a compact, closed form, amenable to numerical investigation, and including the dependence on electron parameters such as effective mass and gyromagnetic ratio. Effects due to the Coulomb interaction are discussed within the limitations of the random phase approximation. The theoretical results are used to predict the conditions that must obtain for the observation of neutron excitation of Landau and collective modes.

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Riassunto La funzione di risposta per lo scattering magnetico dei neutroni dagli elettroni che forma un plasma ad un componente, o modello di jellio, soggetto ad un campo magnetico fisso, è calcolata nel limite semiclassico nel quale la statistica di Boltzmann si applichi agli stati elettronici. Si dà un’espressione completa per la risposta di un plasma ideale in una forma compatta e chiusa adatta alla ricerca numerica e che include la dipendenza dai parametri elettronici come la massa efficace ed il rapporto giromagnetico. Si discutono gli effetti dovuti all’interazione di Coulomb entro i limiti dell’approssimazione di fase random. I risultati teorici sono usati per prevedere le condizioni che devono essere ottenute dall’osservazione dell’eccitazione dei neutroni di Landau e dei modi collettivi.

     

NMR parameters in gapped graphene systems

We calculate the nuclear spin-lattice relaxation time and the Knight shift for the case of gapped graphene systems. Our calculations consider both the massive and massless gap scenarios. Both the spin-lattice relaxation time and the Knight shift depend on temperature, chemical potential, and the value of the electronic energy gap. In particular, at the Dirac point, the electronic energy gap has stronger effects on the system nuclear magnetic resonance parameters in the case of the massless gap scenario. Differently, at large values of the chemical potential, both gap scenarios behave in a similar way and the gapped graphene system approaches a Fermi gas from the nuclear magnetic resonance parameters point of view. Our results are important for nuclear magnetic resonance measurements that target the ¹³C active nuclei in graphene samples.     

Turbulence in systems with small parameters

Turbulence in systems where small parameters intervene, mainly through the interaction subsystem-environment, is described. The relaxation has typical features which determine experimental results. Fluctuations can be calculated and phase transitions can be predicted.     

Determination of the best carrier frequency based on the system and environmental parameters in underwater acoustic systems

One of the most challenging features of underwater acoustic (UWA) channel in comparison with its terrestrial radio frequency counterpart is highly frequency-dependent path loss. Thus, utilizing efficient carrier frequencies in UWA systems can considerably reduce the path loss. In this context, this paper presents an approximate formula for determining the best carrier frequency based on both the system and environmental parameters. To achieve this goal, this research first addresses a simple algorithm including general steps for tuning the parameters of Francois and Garrison (FG) formula in the frequency range of 10 to 100 kHz based on the appropriate experimental data which can be acquired from any interest region. Second, for a more accurate modeling of path loss, this paper considers the loss due to the reflections of sound from both the rough surface and bottom of the sea by employing the ray theory. Third, this study presents a general algorithm for modification of the power spectral density (PSD) of ambient noise based on Wenz formula in the frequency range of 10 to 100 kHz and the required experimental measurements which can be simply collected from any interest channel. Moreover, it is mathematically demonstrated that the ambient noise in the frequency range of 10 to 100 kHz, can be generally approximated with a strict sense stationary (SSS) colored normal stochastic process which is ergodic not only in mean and covariance but also in distribution. Finally, an approximate formula for the best carrier frequency is derived by maximizing the sound to noise intensity ratio (SNR). To verify the validity of simplifications and approximations utilized in this study and to assess the performance of our proposed algorithms and formulas, experimental results obtained in the Strait of Hormuz (SoH) are compared with the original, simplified, and modified models under different scenarios.